On beta wiki, choose Close topic, enter a summary, click the Preview button
- you're taken to a new page instead of an inline action
- it doesn't actually preview and the text in the textarea is lost
- the new page always shows "There seems to be a problem with your login session; this action has been canceled as a precaution against session hijacking. Go back to the previous page, reload that page and then try again"
If you try to preview on this external page, it immediately closes the topic with the summary you entered.
FWIW in the recent past Preview has shown a preview inline but turned Cancel italic, and/or immediately performed the close action.